What is a Flap Disc?

Flap Discs are designed to increase work productivity and reduce overall cost by grinding, blending and finishing in 1 step. Flap Discs are constructed by layering coated abrasive flaps so when a flap wears away, a new flap will be expose with fresh, sharp abrasive grains.

Flap Disc Basics

There are 4 basics components of a flap disc: Backing Shape, Backing Type, Gain Type & Density.

Backing Shape

Type 29 – Conical Shapeflap-conical-300x71

  • Built-in angle for increased contact area
  • Best for use on contoured surfaces and edge work
  • Minimizes workpiece gouging
  • More aggressive stock removal due to higher angle
  • 15°-25° working angle

Type 27 – Flat Shapeflap-flat

  • Best for use on miter joints, corners and edges
  • Best choice for finishing intricate and ornate surfaces
  • Ideal for smooth finishing
  • 0°-15° working angle

Backing Type

Fiberglass Backingfiberglass-backing

  • Backing will wear uniformly with abrasive cloth
  • Will not splinter or smear on the workpiece
  • Lighter, quieter operation

Plastic Backing

  • Non-scratching, high strength backing
  • Resistant to temperature extremes, common chemicals and solvents
  • Some plastic backings are trimmable

Flap Backing: Polyester, Polyester-Cotton or Cotton

  • Polyester
    • Able to withstand extremely high pressure without degrading the flap
    • For extreme stock removal and edge grinding
  • Cotton
    • Used where maximum conformability and soft feel is the goalplastic-backing
    • Must be used under lighter pressure to maximize performance and life
  • Polyester/Cotton Blend
    • The best of both worlds
    • Can withstand high pressure while still maintaining good stock removal and finishing
    • Often used as the starting point for flap disc operations for first time users

Grain Type


  • This allows for a consistent under a wide variety of grinding applications
  • You should consider opting for a ceramic disc when grinding on steel, stainless steel or aluminum
  • Ceramics also tend to grind cooler minimizing discoloration while maximizing product life


  • These discs are used for general steel grinding, stock removal and finishingflap-regular
  • The economical choice when cost is the driving factor


High density flap discs provide the user with approximately 40% more grinding material. This increase in grinding material leads to increased flap-highproductivity and longer life.

Choose Flap Disc Over..

Flap Discs Over Grinding Wheels

  • Faster stock removal and smoother finish
  • Quieter operation and reduced vibration minimizing operator fatigue
  • Cooler cutting, reduced loading and glazingflap-discs
  • Easy to use – reduced gouging and rework

Flap Discs Over Fiber Discs

  • Up to 20 times longer life than a fiber disc
  • No backing pad needed
  • Easier storage – no curling
  • More consistent finish

What Makes United Abrasives Better than the Competition

Check back for our next blog post, “United Abrasives Flap Discs, the Professional’s Choice“, to learn why professionals choose United Abrasive Flap Discs over the competition!